Gas Water Heater burner won't stay on

[golferac]

Interesting issue popped up this morning. No hot water. It's a gas hot water tank with an automatic igniter. Followed the steps, the pilot light lit in both the Pilot and Low knob positions. Put it in the ON position and adjusted the heat knob and the burner fired "whoooosh" and everything was good. Left the room, and heard a weird clicking sound 2 minutes later. Went back and the pilot light was out. Redid the steps, everything was excellent until 5 seconds after the burner ignited then "click" off. Interwebz indicated that this might be a thermocouple (temp sensor) issue but before I make a trip to HD, I'd like to ask if there is anything else I should consider or if anyone else has gone through this. Venting seems ok and all screens seem clean so I am not sure if this is a thermocouple issue or O2/gas/flame mixture issue. Any input is greatly appreciated.

[CaberTosser]

A solid possibility is that the FVIR sensor is tripped. It’s a small safety switch that’s mounted on the burner mounting plate with two wires connected to it. If you have a multimeter you can check for conductivity across it. They’re problematic things, more often defective than shutting off for actual safety issues.

To test that, do a temporary bypass of it by putting the two wires together & see if it fires normally. If so, undo the testing bypass, snag a new switch from Amre Supply or wherever you can find that carries your brand & install it

Generally not a hardware store part, at least that I’ve ever seen

[barbless]

If you can get the thermocouple out try and clean it with a rough cloth or scratch pad. Do not use anything really abrasive like steel wool. Put it back in and try again. You might be able to do it without taking it out. I'm no expert

[CaberTosser]

Originally Posted by barbless

If you can get the thermocouple out try and clean it with a rough cloth or scratch pad. Do not use anything really abrasive like steel wool. Put it back in and try again

Cleaning a thermocouple does exactly nothing. They’re either dead or not. The usual issue with them is either not having the flame impinging over them correctly (bad placement of tip in flame) or a dirty/weak yellow pilot flame (pilot burner needs cleaning as it’s not hot enough for the thermocouple/thermopile to generate the required voltage). Usually a weak burner has the air premix pathway blocked by lint & dust


Cleaning is more for flame sensor probes

Current water heaters have sealed burners & are more of a PITA to remove & service those components, one wants to keep it properly sealed to retain the fire safety function of the flashback arrestor / air inlet screen

[elkhunter11]

I had to clean the flame sensor on my hot water heater in December, about 15 minutes to remove, clean and reinstall. I used a small brass welding brush from Canadian Tire.

[CaberTosser]

Originally Posted by elkhunter11

I had to clean the flame sensor on my hot water heater in December, about 15 minutes to remove, clean and reinstall. I used a small brass welding brush from Canadian Tire.

When it has a pilot light, it won’t have a female sensor. The brass brush is correct for flame sensors though.

[CaberTosser]

Originally Posted by CaberTosser

When it has a pilot light, it won’t have a female sensor. The brass brush is correct for flame sensors though.

lol @ 'female sensor'. Can't edit it so I'll have a chuckle instead

[Mountain Guy]

Originally Posted by CaberTosser

lol @ 'female sensor'. Can't edit it so I'll have a chuckle instead

yes totally incorrect.... a flame sensor would be more of a male sensor than a female sensor..

[dewalt18]

I just attempted cleaning my female sensor with a brass brush. It’s cleaner for sure, but won’t ever do that again. . .

[CaberTosser]

Originally Posted by dewalt18

I just attempted cleaning my female sensor with a brass brush. It’s cleaner for sure, but won’t ever do that again. . .

Like this, but brass? What drill speed did you use? That might have been the issue...

[dewalt18]

Originally Posted by CaberTosser

Like this, but brass? What drill speed did you use? That might have been the issue...

Similar, but notably smaller in both depth and diameter 😂

[barbless]

WHOA not brass. Yes it is a female cleaner LOL. Battery terminal cleaner. The little pencil "D" would not even touch the sides. HA HA Family show

[golferac]

I thought I posted but apparently not. A big thank you to everyone. I cleaned the sensors and thermocouple with 400 grit sand paper. There was a white residue on the parts but that buffed out easily. Put everything back together and everything worked until a few hours ago. Now the pilot light lights but as soon but won't stay on. So now it's off to Lowes for a Honeywell thermocouple and we will try again.

[Dewey Cox]

It has been a long time since we've had a "clean your thermocoupler" thread on here.
I thought it had been mocked into extinction.